Let's Find the Maximum Value !

Let $S$ = $\frac { x sec x }{ 12x^{2} + 3 +12x^{2} tan x^{2} }$ for 0 $<$ $x$ $<$ $\pi$

The maximum value of $S$ can be written as $\frac {a}{b}$ , where $a$ is relatively prime with $b$

Then, What is the value of $a$ + $b$ ?